Types & Classes of Warships

Generally, nomenclature for types of U.S. Navy vessels is rather distinctive. For example, the terms frigate, ship-of-the-line, sloop-of-war, and ironclad, are indicative of different classes of 18th and 19th century warships that vary by tonnage, armament, and rigging. "Battleship," in conjunction with a hull number such as BB-1, indicates a 20th century warship. However, the same term may refer to very different types of vessels. Sloop may mean a small, one-masted, fore-and aft-rigged sailing vessel, or a sloop-of-war. A steamer could refer to steam-powered vessels employed in any number of distinct naval activities such as tender, tug, or transport. The class designation YC referred to a coal barge in the 1920s, but in the 1930s, it was used for open-lighters. Also, different terms were used to refer to a single ship. The same vessel might be called a galley in one document and a gunboat in another. This could mean that it was a galley acquired by the Navy and converted to a gunboat, or it could refer to a specific class of warship built to a galley design. The same steam-powered frigate with screw propulsion may be called a screw steamer, frigate, or simply a warship in various documents.

Such problems were particularly evident in, although not exclusive to, 18th and 19th century vessels. This is due in part to less standardization in ship nomenclature, design, and function. While some of these earlier vessels were built specifically as warships and auxiliaries, many were commercial or private vessels altered for military use. A sailing vessel could be used as a whaler, or converted to a naval gunboat or transport. Many sidewheel steamers were transformed into casemated gunboats. And a vessel could be employed in any number of uses during its naval service. The same steamer could at various times be considered a packet boat, a transport, or a tug, and referred to as such in documentation.

Nomenclature for these early ships is derived from a combination of rig, hull design, propulsion, use, and naval-class descriptions. For 18th and 19th century vessels, a distinction is made between those that were built as a specific class of naval warship or auxiliary, and those acquired by the Navy and converted to naval use. Eighteenth and 19th century ship types were defined by combining descriptions of class, hull type, mode of propulsion or armament configuration, such as screw frigate or ironclad ram.

Ships of the steam navy can be divided into two major categories: armored and unarmored, and a third for miscellaneous vessels. Terms indicating armored vessels describe major distinguishing visual elements of a ship's armor, hull design, or armament. Terms for unarmored steam vessels indicate class of warship or hull design, and mode of propulsion. Nomenclature for 19th century armored vessels is varied and inconsistent. Therefore, instead of deriving terms directly from documentation, as with the sailing vessels, synthesized and simplified terminology was developed specifically for the database. The terms are broken down into three general categories that include: ironclads, monitors, and other types of armor. Within each category, there were several design variations. These terms adequately describe most 19th century armored vessels

The "Dreadnought" (British) was the first battleship to carry all big guns (12-inch), supplemented by a rapid-fire battery (3-inch) for torpedo attack. In dispensing with the intermediate armament, 6 to 9-inch, carried by battleships prior to this time, the "Dreadnought" was enabled to carry a greater number of large guns. Battleships antedating the "Dreadnought" were termed "pre-Dreadnought." Battleships constructed since are generally of the "Dreadnought" type (all big guns, with rapid-fire guns). The larger ones, carrying larger guns, 14- to 15-inch, are termed "super-Dreadnought."

The battle cruiser was essentially a battleship, but with the higher speed necessary for advance skirmishing and for pursuit. To attain this speed, it was necessary, in order to install heavier engines and boilers, to sacrifice, to a small extent, armament and armor protection. The armored cruiser has high freeboard, lighter armament and armor than battleships, but greater speed than battleships of the same period.

Cruisers have high freeboard in contra-distinction to battleships, were intended for patrol purposes, and carry light guns and in some cases light armor. The faster cruisers are termed "scouts" and are used to accompany or precede the fleet on scouting duty. Those haying protective decks and no side armor are termed "protected cruisers." The small ones used in shallow waters were termed "gun boats," and have low speed and no armor.

Battleships can be distinguished from armored and light cruisers by their more massive appearance, particularly in the superstructure of turrets, guns, and cranes, by their lower freeboard and broader beam, and by their more irregular silhouette. Dreadnoughts can be distinguished from the older battleships by their size, but can not be distinguished from the larger battle cruisers.

Monitors were intended for the first line of battle. Their chief characteristics were the revolving turrets mounted on a heavily armored hull of extremely low freeboard. The type was obsolete by the time of the Great War and would be used for coast defense only, though recently monitors have been built and used in rivers and on the coast against the mobile army fortifications and forces.

Torpedo boats were designed for torpedo attack on larger vessels, and possessed great speed, a few small guns, and no armor. They are now used for coast defense purposes, being displaced on the seas by destroyers. Destroyers were designed, originally, to operate against torpedo boats, and possess greater speed latter, but are now used with the fleet for torpedo attack and for defense against submarines.

Submarines were designed for under-water torpedo attack, but may have light guns for service above water; they may also be used against fortifications, as on raids against searchlights, observing stations, and mine fields. They may also be used in cost defense work on patrolling duty, particularly in fogs, and against the hostile fleet.

Until 1920 the nomenclature of a U.S. Navy ship was spelled out (e.g., frigate, sloop-of-war, monitor, torpedo boat, submarine, etc.). Early in the 20th-century, as ship types diversified and became more numerous, the Navy began referring to ships of certain types by a consecutive number indicating the relative order of their construction, applying numbers retroactively back to the beginning of the particular type in question. For instance, the first U.S. destroyer, Bainbridge, was given the number "one" (No.1). Battleships, submarines and torpedo boats were likewise referred to by number, as were some cruisers and monitors. Thus, Pittsburgh was known as Armored Cruiser No. 4; Tonopah as Monitor No. 8; Flusser as Torpedo Boat-Destroyer No. 20; and F-4 as Submarine Torpedo Boat No. 28. In a variation to this practice, register numbers prefixed with the letters "SP" were given to many of the privately owned ships taken into the Navy in World War I. Assigned at the time a ship was inspected and accepted by the Navy, the number bore no relation to the type nomenclature system, but was for identification only.

Following World War I, and the confusion experienced in mailing correspondence and shipping spare parts to ships during the war, Acting Secretary of the Navy Robert E. Coontz approved a standardized system of alpha-numeric symbols to identify ship types (e.g., BB for battleship, DD for destroyer, DM for light mine layer, AD for destroyer tender). Linked with a consecutive number, the use of which now became general for all types of naval ships, these classification symbols provided positive and individual identification of both named and unnamed ships, many of which might not be readily identifiable by name alone.

As with any retroactively applied system, peculiarities and seeming discrepancies were bound to (and still do) appear. George Washington (SSBN-598), for example, was a fleet ballistic missile submarine, nuclear propulsion, with a hull number of 598. This seems to indicate that George Washington was the 598th ballistic missile submarine accepted by the Navy, a reasonable assumption given the mid-20th century practice of using consecutive numbers. This is not the case, however, as the numbers were consecutive by general type, not individual class variations. Thus, SSBNs were slotted into the "submarine" category along with every other variation in submarine type (SS, SSK, SSG, SSN, etc.). George Washington, therefore, received number 598 even though it was actually the first SSBN in the U.S. Navy. Indeed, that submarine was not even the 598th boat accepted by the Navy, as submarine G-1 (ex-Seal) was assigned the hull number 191/2 to fit it into it's proper place in the chronological listing of submarines. This happened in other cases as well, with second-class battleships Texas and Maine, both originally rated as "armored cruisers," preceding Indiana (Battleship No. 1, later redesignated BB-1). In addition, some hull numbers were assigned only to have the ship contract canceled. The slots remained empty so as not to give lower hull numbers to younger ships.

Significantly, the U.S. Navy later altered the tradition of consecutive numbering with the launching of some new or converted classes of ships in the 1950s and beyond, though this initially began during World War II with the Alaska-class (CB-1) battle cruisers. For example, light cruisers converted to guided-missile cruisers gave up their CL numbers, with CL-92 becoming CLG-4; the first nuclear-powered cruiser Long Beach was assigned CGN-9 rather than CGN-160 (the next available cruiser number); and the first Oliver Hazard Perry-class frigate received FFG-7 vice FF-1097. The latest changes took place in the 1990s, with the construction of the Seawolf-class SSN-21 boats and work on an experimental DD-21 class of destroyers. This despite having used SS-21 in 1912 and DD-21 in 1898. The peculiarity in hull numbering apparently came about when the project titles were applied as hull numbers, thus, for example, the "Submarine for the 21st Century" became SSN-21.

The Navy also organized ships by type, both for administrative reasons and to have a system in place to make comparisons with foreign navies, as illustrated by the 1919 Office of Naval Intelligence list of definitions. That general delineation was expanded and broken down into individual ship types with the issue of General Order 541 of 17 July 1920, which established the letter-symbol system of ship designation in use today. Designations are grouped within each category by alphabetically arranged letter symbol.

Since type names and designation symbols are subject to change over the years, as the Navy changed in size, structure and composition. SECNAV 5030.1E from 1968, version L from 1993 and SECNAVINST 5030.8 from 2006 illustrate this evolutionary process.

Ship types are listed under the general type categories (Cruisers, Mine Warfare Types, etc.) as they were or are officially assigned. When the letter-symbol system was first established it was intended that the first letter of a symbol should indicate the type category; as, B for Battleships, A for Auxiliary ships, and so on, with the second letter sometimes, but not always, indicating the sub-class. Since the letter-symbol system began in 1920, many exceptions to this principle have arisen. Ships with a letter prefix denoting one category are sometimes assigned to another while retaining the original symbol. Or a new type category will be setup, with types assigned to it from other categories; these types will sometimes retain their old symbols. For example, the category of Mine Vessels, established in 1928, was assigned ships with symbols beginning with A, C, and D; it was not until the 1950's that most minecraft received new symbols prefixed with M. Amphibious warfare types were considered Auxiliary Ships until 1942, when the prefix L was applied to landing ships and craft; but several amphibious types such as the AKA and APA continued to bear the Auxiliary (A) prefix.